This invention relates generally to those products used to provide visual stimuli for testing and to comfort patients undergoing diagnostic treatment and, more particularly, to a video projection system for use by operators and patients during analysis within a magnetic resonance imaging (MRI) or a magnetoencephalography (MEG) apparatus.
The diagnostic device known as magnetic resonance imaging (MRI) has become an invaluable tool for imaging and exploring the internal body without surgery. MRI has the ability to distinguish healthy and diseased tissue, fat and muscle, and between adjacent structures within the body which other modalities cannot demonstrate. MRI utilizes safe radio waves and a magnetic field to generate the images processed by a computer.
In operation, a typical MRI apparatus relies upon hydrogen protons which have a dipole movement and therefore behave as would a magnetic compass. In MRI scanning, the MRI apparatus operates as a large magnet wherein the protons align with the strong magnetic field but are easily disturbed by a brief radio frequency pulse of very low energy so as to alter their alignment. As the protons return to their orientation with the magnetic field, they release energy of a radio frequency that is strongly influenced by the biochemical environment. The released energy as detected and mathematically analyzed for display as a two dimensional proton density image according to the signal intensity of each tissue.
The magnetic coils of the MRI apparatus are permanently fixed within a large structure so as to form a large magnet with a very confining entrance known as the bore. A patient is placed upon a scanner table that is integrated with the MRI apparatus and slid into the middle of the bore. The problem with the bore is the extremely small area for placement of the patient and this leads to anxiety. The large and ominous appearance of the scanner together with harsh low monotone sounds which include both soft and loud thumping, produces an eerie and unnatural experience for the patient. Any patient who exhibits claustrophobic tendencies could require sedation before entering the bore. If the patient is above average in size, the problem is exasperated.
It is well known that familiarity of surroundings reduces anxiety. The introduction of familiar images to a person placed within a confining area, such as the MRI bore, will reduce if not eliminate anxiety and certain claustrophobic tendencies of various patients. This reduction can eliminate the need for medicating the patient or the need for a-restraining device, all of which may have an adverse effect on a diagnostic test. Thus, a patient who is able to listen to a family member, soft music, or watch a familiar television program will have sufficient distractions so as to avoid concentrating of the immediate surroundings which lead to increased anxiety.
In some instances, the diagnostic procedure performed with the MRI is used to evaluate a patient""s response to specific visual stimuli. The operator sends a series of images to a screen which is seen by the patient during the MRI procedure and the patient""s responses are included in the MRI report.
A problem with introducing conventional audio or video signals into an MRI apparatus is that the device is based upon the use of radio frequency which will disrupt signal modulation. Further, the inner area of the bore produces a magnetic field which will draw metal items when magnetized. For this reason, the audio or video signal must be in a form that is not affected by the radio frequency and transmission by a mechanism that is not easily magnetized.
An attempt to address this problem is found in U.S. Pat. No. 4,901,141 which utilizes a fiber optic taper positioned within the bore of an MRI apparatus. A CRT produced image is delivered to the fiber optic taper through a coherent image guide. The fiber optic taper expands the end of the image guide so as to provide a larger viewing surface for the patient. The problem with the fiber optic taper is that it is stationary and the patient must be positioned in a fixed location so as to be able to see the end of the optic taper. Further, to prevent distortion the patient must be located directly beneath the isocenter of the taper. Thus, the disclosure does not address different size patients, patient positioning, or near and far sighted patients For instance, a tall person may lay with their head partially outside the bore during diagnostics of the lower body whereas a child may be well encapsulated by the bore, neither of which could properly see a fixed fiber optic taper. In addition; the use of a fixed taper will interfere with auxiliary coils, such as head and c-spine coils, that require close proximate to the body. Current construction of head and c-spine coils is such that the visual field as needed for viewing a fixed positioned fiber taper is either obscured or completely blocked if the fiber taper is utilized.
Another prior art device is disclosed in U.S. Pat. No. 5,414,459 directed to a pair of glasses worn by the patient. The glasses receive the video picture by fiberoptic guide.
In both theses devices the installation is permanent with a fiberoptic connection between the shielded MRI room and a remote location housing the operating elements of the system. The connection requires the shielding which surrounds the MRI room to be breeched and that penetration must be adequately protected.
Yet another known device utilized in combination with an MRI apparatus for purposes of patient comfort is a mirror optical system mounted on a spectacle frame and secured to the patient""s head. In operation, the patient lies on the scanner table wearing the optical mirror system so that the, patient can view over their head so as to watch a television set placed outside of the bore. The mirror mounted spectacles allow use of a head coil, c-spine, or other skin surface mounted coils. A problem with the spectacle mounted mirror system is that it blocks forward viewing and does not accommodate image tilting should the patient turn their head.
Thus, what is lacking in the art is a device that provides the clarity of reproduction only possible by the close proximity of the patient to the viewing screen. The close proximity allows a small image to provide a large field of view.
Also, lacking in the prior art is an orientation of the screen, in relation to the patient, that permits unobstructed viewing of the entire screen.
In using the prior art viewing devices with the screen outside the bore of the apparatus, the patient""s field of view inherently includes exterior surroundings which can include distractions. Therefore, the prior art lacks a structure which can eliminate the appearance of unintended stimuli.
The present invention satisfies this need through the provision of a magnetically inert and RF shielded LCD projector located closely adjacent the MRI bore. The projector is used with a screen that is located inside the MRI bore near the patient""s head. The short distance between the projector and screen permits a very narrow beam to be passed above the patient and below the top of the MRI bore while providing an unobstructed picture for viewing. The magnetically inert projector is fed the video signal by fiberoptic cable from a source which may be placed within the room but outside the magnetic field of the MRI. In this manner, the entire apparatus is made portable.
The screen is movably placed inside the bore of the MRI in a vertical orientation between the top of the bore and the patient. The screen is of translucent material which allows projection from either end of the MRI bore.
The supine patient views the screen through an adjustable prism or other mechanism having reflecting elements that can change the line of sight through 90 degrees. The viewing device is located in his near field of vision.
The relative closeness of the screen to the patient""s eyes and the projector allows full picture viewing for patients of differing sizes.
Thus, a primary objective of the instant invention is to provide a video within an MRI apparatus to view a visual image that is superimposed on a translucent surface allowing the viewing of the displayed image as well as the immediate surroundings.
Yet another object of the instant invention is to provide an LCD projector that is magnetically inert, RF shielded and is passively cooled without a motorized fan.
Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.